This invention relates to caps for liquid tanks and, more particularly, to caps for liquid tanks, such as fuel tanks for internal combustion engines, which caps have an internal vent system.
Some liquid storage tanks, such as fuel tanks for internal combustion engines, require some sort of system for venting the interior of the tank to atmosphere so that the liquid can be withdrawn from the tank without creating a vacuum condition which can cause stoppage of the liquid flow. This venting often can be provided most conveniently by incorporating a vent system into the cap used for closing the filler neck on the tank because the filler neck usually is located on the top of the tank and is connected to the highest point of the air space in the tank.
When fuel tank caps including an integral vent system are used on outboard motors, it is desirable to provide some means for selectively closing the vent system in order to prevent fuel from leaking from the fuel tank when the motor or tank is removed from the boat. Also, it is desirable to provide some sort of means for preventing sloshing fuel from leaking through the vent during normal operation or when the motor or tank is tilted.
Examples of prior art constructions of fuel tank caps having an integral vent system are disclosed in the following United States patents:
2,666,550 Armstrong et al issued Jan. 19, 1954 PA1 2,800,245 Doyle et al issued July 23, 1957